Intraoperative neurophysiologic sensorimotor mapping and monitoring in supratentorial surgery.

It has been shown that aggressive removal of gliomas improves survival and the quality of life in both adults and children. Conversely, there is a strong correlation between incomplete resection of an epileptic focus and poor seizure control outcome in epilepsy surgery. Thus, it is no surprise that maximal resection of supratentorial lesions remains a priority in neurologic surgery. In many circumstances, this is difficult to achieve because of the close proximity of functionally eloquent regions. As a consequence, accurate identification of the latter is imperative to reliably identify safe boundaries for resection and to expand them as much as possible, while preserving neurologic function. Along these lines, preservation of sensorimotor function, with significant impact on postoperative outcome and quality of life, remains essential as achieving maximal resection. Although there is a wide range of methods that could be used for functional sensorimotor mapping, intraoperative neurophysiologic techniques are still considered by many to be the "gold standard." This article provides a detailed overview of these techniques, their principles, and several alternative methodologies. Although the overview directly reflects the current practice at our institution, it also shows the temporal evolution of the major motor mapping methods, relating them to all significant contributions made over the years by different experts in the field. I have tried to exemplify the relevant points of these techniques by using as many pictures and clinical examples as possible.